Switch



April 16, 1940. c. J. WERNER SWITCH Filed Oct. 21, 1936 2.Sheets-Sheet lApril 16 1940. c. J.- WERNER SWITCH Filed Oct. 21, 1936 2 Sheets-Sheet 2Ina uuztlom W Insulation Patented Apr. 18, 1940 UNITED STATESLPATENTOFFICE- SWITCH Werner, Dayton, Ohio, assignor to General 'MotorsCorporation, Detroit, Mich, a corporation of Delaware ApplicationOctober 21, 1936, Serial No. 106,723 x 20 Claim.

This invention relates to a thermal responsive switch, and moreparticularly to such a switch adapted toprotect an energytranslatingdevice from damage due to overheating.

An object of this invention is to provide a switch for protecting anenergy translating device from overheating, which switch can be easilyand cheaply manufactured and which cannot have the purpose thereofdefeated by the user by u securing the actuating member in some fixedposition. This object is accomplished by providing a switch structurecomprising a small= number of inexpensive parts, including a thermalresponsive latch, that are easyto' assemble l. and by so constructingand arranging theparts that the switch actuating member holds the'switch contacts apart while force is applied thereto to actuate thecontacts, whereupon the con tacts engage upon release of theforce-applied to the actuating member and whereupon one of the'contactmembers is free of the actuating member upon such release of thepressure applied thereto, so that when the thermal responsive latchreleases the said one contact member, the contacts are disengagedirrespective of the position of the acuating member.

Another object of this invention is to provide a thermal responsiveswitch for protecting an energy translating device, which switch isadapted a to receive heat from the energy translating device by virtueof being mounted in heat ,receiving ,relation, therewith and which isadapted to be -provided with 'means adaptable to the energy translatingdevice and the protection desired foradditionally influencing theoperation of the switch. This object is accomplished by providing athermal responsive locking structure that is adapted to have a heatingelement such'as a resistance wire associated therewith and/or a heatconducting element for/conducting heat from apart of the energytranslating device to the thermal responsive locking structure.-

Further objectsand advantages of the present invention will be apparentfrom the following de-' scription, reference being had to theaccompanying drawings wherein a preferred embodiment of the presentinvention is clearly shown. In the drawings: I Fig. 1 is a fragmentaryview of 'a dynamo electric machine equipped with one form,of thermalprotective device embodying the present invention, said devicebelngbroken away to show the interior thereof. The heater element hasbeen omitted for the sake of clearness. r j .i 'igs. 2, 3 and 4 areviews of the thermal protective device minus-its heater element, withparts thereof shown in different positions of operation. These viewsshow the device with the cover removed and looking in the direction ofarrow 2 ,of Fig. 1.

invention different in some details from that shown in Fig. '1. a

Fig. 5 is a view taken in the direction of arrow '5 of Fig. 4 inverted,however, and with the heater element attached.

arrow 6 of Fig. 5.

I Fig. 7 is a sectional view on the line l 'l of mg 5 Y Fig, 8 is asectional view taken on line 8-8 of Fig. 1 and turned through an angleof 90.

Figs. 9 and 10 are perspective views of a modifled form of switchembodying the present invention and indicateone operating position oftheswitch parts as viewed from substantially opposite sides of the switch.a

' Figs. 11 and 12 are also perspective views of the r apart Fig. 6 is aview taken in the direction of the Figs. -2, 3 and 4 show a form of thel2 has. slots i6 and I8 in one end thereof in which a resilient switcharms 20 and 22 respectively areanchored. Connebtoriugs 24 and 26 thatare preferably integral with the switch arms 20 and 22 respectively,extend outwardly from the housing i2 for making electricalconnections tothe switch arms. .The switch arms 20 and 22 extend into the housing i2,out of contact with the walls thereof, and have contacts 28 and 30respectively mounted thereon in alignment for engagement.

The switch arms 20 and 22 are normally biased to positions,substantially as indicated inFlg. 2, such that the contacts 2-8- and '30are out of engagement. The switch arm 20 is preferably longer than theswitch arm 22, sothat it extends beyond the end of the switch arm 22;the switch arm 20 having a pawl 32 provided thereon, preferably bybending the end of the arm 20 in substantially the form of a hook. Theswitch arms 20 and 22 have lugs 34 and 36 respectively on the sidesthereof which are preferablyintermediate the ends of the switch arms.Resilient reinforcleaf springs 36 and 46, preferably made of springsteel and that are substantially the same shape as the switch arms 26and 22 respectively, but somewhat shorter than the switch arms, extendalong one side of those portions of the switch arms that are subject toiiexure, and are anchored inthe slots I6 and I8 in the end of thehousing. These leaf springs 38 and 46 have lugs 4I and 43 thereon thatcorrespond to and are in alignment with the lugs 34 and 36 on the switcharms. The switch arms 26 and 22 and the reinforcing strips 36 and 46each have lugs such as those indicated at 42 and 46 thereon which fitinto cooperating recesses 44 and 41 respectively in the housing I2 toaid in the anchoring of the switch arms and reinforcing springs.

A tubular stud 46 extends through the housing I2 and fits an opening 46in one wall of the housing. A ratchet wheel 66 is rotatably mounted onthe stud 46, and is normally held stationary with respect to the stud bya layer of solder or other similar bonding material at 62 intermediatethe stud and ratchet wheel, which fusible material fuses or melts at atemperature abnormal to the energy translating device with which theswitch is used. The stud 46 and ratchet wheel 56 are located in positionfor latching engagement with the pawl 32 when the switch arm 26 isflexed toward the switch arm 22. Figs. 1 to 7 inclusive indicate thepreferable form of switch for use when it is desirable to have theswitch responsive to current flow through a winding of the energytransferring device with which it is used. A resistance wire heaterelement 64 has one end anchored in an opening 56 at one end of the stud,and extends substantially axially through the hollow stud. This heaterelement 64 is connected into the circuit of the energy translatingdevice by a connecting lead 51 which is electrically connected to theend of the stud 46 and preferably soldered thereto, as at 56, and isalso connected to the connector lug 24 by soldering, as at 66. In theFigs. 1 to 4 the heater element 54 has not been included for the purposeof simplifying the drawings. This heater, however, is shown in Figs. 5,6 and 7.

In a modified form of the switch, such as that shown in Figs. 1 and 8,where it is desired to have the switch responsive to the temperature ofthe windings of the energy translating device for which it is used andto omit the heater element 54, an angular plate 62 of heat-conductingmaterial, such as copper, preferably has the stud 46 extruded from oneside thereof and integral therewith to provide high heat conductivityfrom the plate to the stud. This plate 62 extends along one side ofthe-housing and is preferably mounted against the winding of the energytranslating device, substantially as indicated in Fig. 1, for conductingheat from the winding to the stud. In either case, the stud preferablyextends through an opening 66 in the cover I4 and is riveted over, as at66, to hold one end of the cover I4 in place. Y A manually operableactuating member I6 extends through an opening I2 in the housing I2.

This actuating member 16 has openings I4 and 76 therein, into which thelugs 64 and 36 re-' spectively, extend. In order to have trip-freeoperation of the switch, the opening I4 is preferably larger than theopening'16. That is. these openings are preferably of such size and sospaced that when force is applied to the actuating member I6 which movesthat actuating member and the switch arm 26 to the left, as viewed inFigs. 2, 3 and 4 the contacts 26 and 66 are held apart by virtue of thespacing of the surfaces 16 and I5 of the openings I4 and 16respectively, and the normal bias of the switch arms 26 and 22 andsubstantially as illustrated in Fig. 3. Further, when the pawl 62engages the ratchet 66 to hold the switch arm 26 in a flexed position,the switch arm 22 biases the actuating member to the right as viewed inFig. 3, so that when the pressure on the actuating member III isreleased, the bis of the switch arm 22 against the surface I6effectsmovement of the actuating memberfin the direction of the bias,which movement effects engagement of the contacts. This movement of theactuating member that occurs responsive to the bias-of the switch arm 22to effect engagement of the contacts provides a space between thesurface I6 of the opening I4 and the lug 64, substantially as indicatedin Fig. 4. Hence, when the fusible material that holds the ratchet wheel66 stationary with respect to the stud 46 melts, and the contacts 26 and36 are engaged, the switch arm 26 is free of the actuating member I6, sothat the bias of the switch arm 26 turns the ratchet wheel 66 on thestud 46 to release the pawl 62 from the ratchet wheel 66 and eifectdisengagement of the contacts 26 and 36.

As previously explained, the stud 46 is riveted at 66 to hold one end ofthe lid I4 in place. The other end of the lid is held by a rivet orother suitable fastening means I6 that extends through an opening 66 inthe housing l2 and through an opening 62 in the lid I4 and which isriveted at 63.

As illustrated in Fig. 1, the switch is adapted to be mounted-in heatreceiving relation to an energy translating device 64 having a frame orhousing 66 and an end head 66. The switch I6 is secured or tied thereinin such a position that the heat conducting plate 62 is against the endturns 61 of the windings of the energy translating device and theactuating member I6 extends outwardly through an opening 66 in the endhead. Theactuating member is thus accessible from the cut side of theenergy translating device for manual resetting of the switch to contactclosed position. A bezel 96 is preferably provided around the opening66.

It is understood that when desirable for use with a particular form ortype of energy translating device, the heat conducting plate 62 can beused in conjunction with a heating element such as 54. heating element54 is preferably mounted within the housing of an energy translatingdevice in such a position that it is influenced by heat from the energytranslating device.

With particular reference to Figs. 9 to 13 inclusive, similar referencenumerals refer to similar parts. In this form of switch, a base I66 ofany suitable insulation material, has switch arms I62 and I64 securedthereto by rivets I66 and I68 respectively, or other suitable fasteningmeans. The ends of the switch arms I62 and I64 that are secured to thebase I66 are preferably separated, and the switch arms preferably extendangularly toward each other so that the free ends thereof are near oneanother. An angular contact member III having a contact portion II2 thatextends toward the switch arm I64 is secured to an end portion II4 ofthe switch arm I62 by a rivet H6 or other suitable fastening means. Theportion II4 of the switch arm However, a switch incorporating the I02 isangularly disposed with respect to the rest of the switch arm. A stud His secured to an angularly disposed end I of the switch arm I04 byriveting the end of the stud at I22. A shoulder I24 on the stud II8engages the side of the portion I20 of the switch arm I04 opposite theriveted portion I22 of the stud. The

stud H8 is preferably hollow, and has a contact support I26 secured inan opening, I28 in the end portion I30 of the stud opposite the rivetedend thereof, so that the contact support I26 extends through the hollowstud substantially coaxially therewith and projects from the endthereof. This contact support I26v is made of resistance material andprovides a heating element when it is desired to have the stud heated inaccordance with the current flow through the switch. If such heating isnot desired, the stud is made of a material of higher conductivity. Acontact I32, preferably having a substantially circular contact surfaceis secured to the projecting end of the contact support I26 in alignmentfor engagement with the contact H2. The switch arms I02 and I04 arepreferably inherently resilient and are so biased that the contacts H2and I32 are normally out of engagement.

A ratchet wheel I34 is rotatably mounted on the outer surface of thestud H8. and is normally bonded to the stud and held in a fixed positionrelative thereto by a layer of fusible material I36 that is preferablyintermediate to the stud H0 and the ratchet wheel I34. This fusiblematerial, such as solder, melts at a temperature abnormal for the devicewith which the switch is used, and which the switch protects. An arm I38which is preferably integral with the switch arm I04 is bent at the endthereof to provide a pawl I40 which engages the ratchet wheel I34 tohold the switch arm I04 in a flexed position such that the contacts H2and I32 are engaged. The arm I38 is preferably integral with the switchI04 so that the switch arm I04 and the arm I38 cannot turn relative toeach other to effect disengagement of 'the pawl from the ratchet wheeldue to causes such as vibration. When the fusible material is melted byexcessive heat, the normal bias of the switch arm I04 effects a turningmovement of the ratchet wheel I34 on the stud H8 and a consequentrelease of the ratchet wheel from the pawl I40, whereupon the switcharms assume positions substantially as indicated in Figs. 9 and 10.

A manually operable actuating member I42 is slidably mounted adjacentthe switch arms I02 and I04 in a suitable support such as that indicatedat I44 which may be the end frame of a dynamo electric machine. Theactuating member I42 is movable toward or away from the switch arms I02and I04, and has a flange portion I46 which acts as a stop to preventthe actuating member from coming out of the support I44 and issufficiently large to engage both of the switch arms I02 and I04. 1

Upon movement of the actuating member I42 toward the switch arms I02 andI04, and the continued movement thereof in that direction, the flangeI46 engages the arms I02 and I04 to effect movement of both of the armsagainst the normal bias thereof The arm I04 is thus moved to such aposition that the pawl I40 engages the ratchet wheel I34 to preventreturn movement of the switch arm I 04. By virtue ofthe differences indistances between the contacts H2 and I32 and the parts of the arms I02and I04 respectively which engage the flange I44, the contacts 2 and I32are held apart as long as sufficient force isapplied to the actuatingmember I42 to overcome the bias of the arm I02. That is, by movement ofthe actuating member I42 which effects engagement of the ratchet wheelI34 with the pawl I40, the switch arm I02 moves to a position such asthat indicated in solid lines in Fig. 11. Upon release of the pressureupon the actuating member I42, so that the contact arm l02 moves theactuating member in the direction of the bias of that arm, the arm I02and actuating member I42 return to a position such as that indicated bythe dot-and-dash lines in Fig. 11; whereupon the contacts engage asindicated in Fig. 12. When the contacts are in engagement, there issuflicient space between the switch arm I04 and the flange I46 that thearm I04 is free of the actuating member and disengagement of thecontacts will follow a release of the ratchet wheel from the pawl,

Both of the forms of the switches disclosed herein are similar inprinciple and operation; and both are adapted to be mounted in heatreceiving relation to an energy translating device, such as a dynamoelectric machine, so that the' fusible material that normally holds theratchet wheel in place is melted by excessive heat from the energytranslating device. That is, each of the switches is adapted to bemounted, for instance, within the end frame of the motor, so that theactuating member extends thru the switch cannot be defeated by tying orsec'ur-' ing the actuating member in any position. Sufficient forceapplied to the actuating member of either of the forms holds thecontacts apart. When sufficient force is applied to the actuatingmember, one switch arm, in each case, is, locked I in a substantiallyfixed position by engagement of the pawl and ratchet wheel while thecontacts are held apart. pawl and ratchet wheel, the release of theforce applied to the actuating member permits a return movement of theactuating member and one of the switch arms by virtue of the bias ofthat latter mentioned switch arm. until tliecontacts engage. The portionof the actuating member which engages the locked switch arm having movedaway from the locked switch arm during After the engagement of the thereturn movement effected by the bias of the other switch arm, aclearance is provided between the locked switch arm and the actuatingmember which is sufficient to permit separation of the contacts uponrelease of the pawl from the ratch et wheel. It is thus clear thatsecuring the actuating member in some positions will hold the conit isto be understood that other forms might be adopted, all coming withinthe scope of the claims device; means engaging the ratchet wheel to holdthe arms in contact engaged position against the normal biasing force ofthe arms; a manually operable actuating member for moving one of thearms to contact engaged position, said actuating member holding the armsapart so that the contacts cannot engage while manual force is appliedthereto.

2. A thermal responsive switch for the protection of an energytranslating device comprising, in combination, a base; a pair of switcharms each having one end anchored to the base and each having a contactthereon in alignment for engagement with the contact on the other arm,said arms being normally biased to positions such that the contacts aredisengaged; a locking element; means movably supporting the lockingelement, said locking element being normally held stationary by amaterial that is fusible at an abnormal temperature of the energytranslating device; means engaging the locking element and adapted tohold the arms in contact eng ged p sition against the normal biasingforce oi. the arms; a manually operable actuating member for effectingengagement of the last mentioned means with the locking element, saidactuating member holding the arms apart during movement towardengagement of said locking element with the last mentioned means anduntil said actuating elementis effectively released, one of said armsbeing free to move from the contact engaged position upon release ofsaid means from the locking element even when the actuating element isheld in any position which permits engagement of the contacts.

3. A thermal responsive switch for the protection of an energytranslating device comprising, in combination, a base; a pair of switcharms each having one end anchored to the base and each having a contactthereon in alignment for engagement with the contact on the other arm,said arms being normally biased to positions such that the contacts aredisengaged; a stud in heat receiving. relation with the energytranslating device, a ratchet wheel mounted on said stud and adapted torotate with respect thereto, said ratchet wheel being normally preventedfrom rotation with respect to the stud by a layer of materialintermediate the stud and ratchet wheel that is fusible at an abnormaltemperature; a pawl adapted to engage the ratchet wheel to hold one ofthe arms against movement in the direction of the normal bias thereof; amanually operable actuating member for moving the said one of the armsto eilfect engagement of the pawl and ratchet wheel, said actuatingmember holding the arms apart while force is applied thereto sufficientto overcome the bias of one or both of said arms, said contacts engagingupon release of the actuating member, and said contacts breaking uponfusing of said material and resulting release of'said one of the armsregardless of the position of the actuating member within the limits ofmovement thereof which permit engagement of the contacts.

4. A thermal responsive switch for the protection of an energytranslating device comprising, in combination, a base;' a pair of switcharms each having one end anchored to the base and each having a contactthereon in alignment 1 for engagement with the contact on the other 7arm, said arms being normally biased to positions such that the contactsare disengaged; a stud in heat receiving relation with the energytranslating device, a ratchet wheel mounted on 1 said stud and adaptedto rotate with respect thereto, said ratchet wheel being normally presvented from rotation with respect to the stud wheel, said-actuatingmember holding the arms I apart while force is applied theretosuiiicient to overcome the bias of one or both or said arms, saidcontacts engaging upon release of the actuating member, and saidcontacts breaking upon fusing of said material and the resulting 112- Ilease of said one of the arms regardless of the position of theactuating member within the limits oi movement thereof which permitengagement or the contacts.

5. A thermal responsive switch for the protec- 4 tion of 'an energytranslating device comprising, in combination, a base; a pair of switcharms each having oneend anchored to the base and each having a contactthereon in alignment for engagement with the contact on the other arm,

said arms being normally biased to positions such that the contacts aredisengaged; a stud in heat receiving relation with the energytranslating device, a ratchet wheel mounted on said stud and adapted torotate with respect there- I to, said ratchet wheel being normallyprevented from rotation with respect to the stud by a layer of materialintermediate the stud and ratchet wheel that is fusible at an abnormaltemperature; a heating element comprising a resistance wire forimparting heat to the stud in addition to that received from the energytranslating device, by virtue of being in heat receiving relationtherewith, a pawl adapted to engage the ratchet wheel to hold one of thearms against movement in the direction or the normal bias thereof; amanually operable actuating member for moving the said one of the armsto eii'ect engagement of the pawl and ratchet wheel, said actuatingmember holding the arms apart while 1 force is applied theretosuiiicient to overcome the bias of one or both or said arms, saidcontacts engaging upon release of the actuating member, and saidcontacts breaking upon fusing of said material and the resulting release7 of said one oi the arms regardless of the position of the actuatingmember within the limits of movement thereof which permit engagement ofthe contacts.

6. A thermal responsive switch for the protection of an energytranslating device comprising, in combination, a base; a pair of switcharms each having one end anchored to the base and each having a contactthereon in alignment for engagement with the contact on the other am,said arms being normally biased to positions such that the contacts aredisengaged; a stud secured to the base; a locking element movablymounted on the stud and normally held in one position by a layer offusible material intermediate the stud and locking element; one of saidarms having a pawl thereon adapted to engage the locking element to holdthe arm againstmovement in the direction of the biasing force of thearm; a manually operable actuating member for effecting engagement ofthe pawl and locking element to hold the contacts in engaged position,said actuating member engaging both of the arms to hold them apartduring movement in the direction effecting engagement of the pawl andlocking element; the other of said arms being biased to effectengagement of the contacts upon release of the actuating member, thesaid one of said arms being free of the actuating member to move uponrelease of the pawl when the contacts are engaged.

7. A thermal responsive switch for the protection of an energytranslating device comprising in combination, a base; a first switch armanchored at one end and having a contact mounted near the other endthereof; a second switch arm anchored at one end and having a contactmounted near the other end thereof, said contacts being in alignment forengagement and said arms being normally biased to positions such thatthe contacts are out of engagement; a stud; a ratchet wheel rotatablymounted on the stud and normally bonded to the stud by a layer offusible material; means engaging the ratchet wheel to hold the firstswitch arm against the normal bias thereof, the

being free of the actuating member upon engagement of the contacts.

8. A thermal responsive switch for the protection of an energytranslating device comprising in combination, a base; a first switch armanchored at one end and having a contact mounted near the other endthereof; a second switch arm anchored at one end and having a contactmounted near the other end thereof, said contacts being in alignment forengagement and said arms being normally biased to positions such thatthe contacts are out of engagement; a stud secured to the base; aratchet wheel rotatably mounted on the stud and normally bonded to-thestud by a layer of fusible material; a pawl on the end of the first armadapted to engage the ratchet wheel to hold the first switch arm againstthe normal bias thereof; the second switch arm being biased to effectengagement of the contacts when the pawl engages 'the ratchet wheel; amanually operable actuating member adapted to move the first arm to aposition of engagement of the pawl with the ratchet, said actuatingmember engaging the second arm during movement of the first arm towardengagement of the pawl with the ratchet to hold said arms apart, saidsecond arm being biased to effect engagement of the contacts uponrelease of the actuating member, said first arm being free of theactuating member when the contacts are engaged.

9. A thermal responsive switch for protecting an energy translatingdevice from damage due to excessive heat comprising, in combination, abase; a first switch arm anchored at one end and having a contactmounted at the other end thereof; a second switch arm anchored at oneend and having a contact mounted at the other end thereof in alignmentfor engagement with the contact on the first arm, said arms beingnormally biased to positions such that the contacts are out ofengagement; a stud secured to one of the arms; a ratchet wheel rotatablymounted on the stud and normally bonded to the stud by a layer ofmaterial that is fusible at an excessive temperature of the device;means engaging the ratchet wheel to hold the said one switch arm againstthe normal.

bias thereof and in a position such that said contacts are biased intoengagement; a manually operable actuating member adapted to effect eningan energy translating device from damage due to excessive heatcomprising, in combination, a base; a first switch arm anchored at oneend and having a contact mounted at the other end thereof; a secondswitch arm anchored at one end and having acontact mounted at the otherend thereof in alignment for engagement with the contact on the firstarm, said arms being normally-biased to positions such that the contactsare out of engagement; a stud secured to the first arm; a ratchet wheelrotatably mounted on the stud and normally bonded in a fixed position bya layer of material that is fusible at an excessive temperature of thedevice; a pawl adjacent the first arm for engaging the ratchet to holdthe first arm against the normal bias thereof and in a position that thesecond arm biases the contacts into engagement; a manually operableactuating member adapted to effect engagement of the. ratchet with saidpawl, said arms and actuating member being so constructed and arrangedthat the contacts are held apart by force exerted upon the actuatingmember, said first arm being free to move with respect to the actuatingmember to effect disengagement of the contacts when the saidmaterialfuses at an excessive temperature.

11. In a thermal responsive switch, asubassembly comprising, incombination, a resilient of the switch arm, a ratchet mounted on thestud and adapted to rotate with respect thereto, said ratchet beingnormally prevented from rotation .withrespect to the stud by a layer ofmaterial intermediate the stud and ratchet that is fusible at abnormaltemperature, an arm integral with the substantially stationary portionof the switch arm and having a pawl thereon adapted to engage theratchet to hold the switch arm against the normal bias thereof. 13. In athermally operated switch, a pair of resilient contact arms normallybiased to open circuit position, a thermally responsive ratchet mountedon one of said arms and adapted to latch the other arm theretoso thatthe latched arm forms a closed circuit, said thermally responsiveratchet upon obtaining a predetermined temperature releasing the arms sothat they may assume an open circuit position.

14. In a thermally operated switch, a pair of resilient contact armsbiased to open circuit position, a thermally responsive ratchet carriedby one of said arms, latching means adapted to engage the ratchet sothat the contact arms are held in closed circuit position, said ratchetupon obtaining a predetermined temperature disengaging from said meansand releasing the arms so that the arms assume an open circuit position.

15. In a thermally'operated switch, a pair of resilient contactarmsbiased to open circuit position, a thermally responsive ratchet carriedby one of said arms, latching means adapted to engage the ratchet sothat the contact arms are held in closed circuit position, said ratchetupon obtaining a predetermined temperature disen-' gaging from saidmeans and releasing the arms so that'the arms assume an open circuitposition, and means for resetting the arms in closed circuit positionafter release.

16. In a thermal responsive switch, a spring terminal member, and aspring contact member. said members being normally biased to opencircuit position, thermal means carried by the terminal member includinga portion adapted to engage the contact member and to latch the contactmember and the terminal member in closed circuit position, said thermalmeans being adapted to release said members so that they may assume anopen circuit position upon the attainment of a predeterminedtemperature, and an operating member for resetting said contact memberand said terminal member in closed circuit position, said operatingmember being adapted to open circuit the contact member and the terminalmember at will when said members are in latched relation.

17. In a thermally operated switch, a pair of resilient contact armsnormally biased to open circuit position, thermally responsive meanscarried by one of said arms and adapted to latch the other arm theretoso that the biased arms form a closed circuit, said means upon obtaininga predetermined temperature releasing the arms so that they may assumeopen circuit position.

18. A circuit breaker comprising two cooperating' contact bladesnormally biased to circuit open position; an actuator engaging both ofsaid blades and adapted to move both blades simultaneously out of normalposition while maintaining them separated; a detent; thermal meanscarried by the one blade and adapted to engage the detent to retain saidone blade in actuated position, said means being adapted also to releasethe said one blade at a predetermined temperature; and means on thesecond blade for engaging the retained blade when the actuator isreleased.

19. A circuit breaker comprising two flexible contact blades normallybiased to circuit open position; a detent formed integrally with one ofsaid blades; a thermally responsive ratchet carried by the second bladeand adapted to engage the detent to retain said second blade in anactuated position below a predetermined temperature; and an actuatoradapted to engage both of said blades and to move both bladessimultaneously while holding them separated, the said one blade beingadapted to engage the retained second blade only when the actuator isreleased after being operated.

20. A circuit breaker comprising two flexible contact arms normallybiased to circuit open position; an actuator, engaging said arms andadapted to move both simultaneously out of normal position whilemaintaining them separated, and thermal means on one of said armsadapted to engage a portion of the other arm to provide ior engagementof both of said arms when the actuator is released.

CALVIN J.

